SQL convert unix timestamp to date

SelectDateFromTimestamp.sql

-- To select min max dates
select 
  dateadd(S, min([time])/1000, '1970-01-01') as startdate, 
  dateadd(S, max([time])/1000, '1970-01-01') as enddate   
FROM HistoricTable

-- To add a calculated column per row
BEGIN TRANSACTION
GO
ALTER TABLE HistoricTable ADD
	ConvertedDate  AS (dateadd(second,[time]/(1000),'1970-01-01'))
GO
COMMIT